Nucleophilic reactions of NAD ion, the coenzyme involved in many biological oxidation-reduction reactions in the living cell, will be studied. The activity to the hydration of NADH to NADHX by a key enzyme involved in glycolysis, a process by which energy is produced for cancer and muscle cells, will be evaluated. This enzyme is glyceraldehyde phosphate dehydrogenase. The role of NADHX as a possible regulatory agent in cell metabolism will be determined. An attempt will be made to isolate and characterize the NADHX reversing enzyme, which catalyzes the reversal of NADHX to NADH. The use of nucleophilic addition complexes of NAD ion will be studied as a convenient tool to understanding the enzymes involved in lactic acid production and in alcohol oxidation, lactate dehydrogenase and alcohol dehydrogenase.